How To Size Air Conditioner Unit
Properly sizing an air conditioning unit for your room can help you save money both by minimizing your electric bill and by decreasing the wear on the AC unit.
If you select a room air conditioner that is too large, the unit will cycle on and off, increasing wear and tear and using more energy.
If it is too small, your room air conditioner unit will be overworked, meaning it is more likely to break down.
The size of an air conditioner unit is shown in British thermal units or Btu which measures its cooling capacity.
How to Size Air Conditioner Unit
Calculate square footage of your room
Calculate the square footage of your room. First, measure the length and width of your room you want to cool in feet. Then, multiply the length times the width to calculate the square footage. For example, if your room is 25 feet by 13 feet, your square footage is 325 square feet.
Use a room sizing chart
Use a room sizing chart, such as the one provided by the Department of Energy, to determine the base number of Btu needed. The larger the room, the more you will need. For example, if your room is 325 square feet, you would need a base Btu of 8,000.
Multiply base Btu from Step 2 by 0
Multiply the base Btu from Step 2 by 0.1 if the room is very shaded or very sunny.
If the room is shaded, subtract the result from the base Btu requirement.
If the room is sunny, add the result to the base Btu requirement.
For example, if your 325-square-foot room is very sunny, you would multiply 8,000 by 0.1 to get 800 and then add the 800 to the 8,000 to find you need 8,800 Btu.
Add 600 Btu for each person beyond the second who will stay in the room to the result from Step 3.
For example, if three people will stay in the sunny room, you would add 600 Btu to 8,800 Btu to find you need 9,400 Btu.
Add 4,000 Btu if the room will be used as a kitchen.
If not, use the total from Step 4 to guide your purchasing decision.
Add 600 Btu for each person beyond the second who will stay in the room to the result from Step 3.
For example, if three people will stay in the sunny room, you would add 600 Btu to 8,800 Btu to find you need 9,400 Btu.
Add 4,000 Btu if the room will be used as a kitchen.
If not, use the total from Step 4 to guide your purchasing decision.